Thus, based on the variability of response in SCA patients treated with HU and the effect of SNPs on the metabolism of drugs, we investigated the influence of SNPs CYP2E1 −1293G>C/−1053C>T, MPO −463G>A, NQO C609T, and GSTT1/GSTM1 on laboratory parameters in SCA patients treated with HU. The gene discussed is CYP2E1; the disease is autosomal dominant cerebellar ataxia.